Mac Address

No its not possible as each Network card has a unique MAC or hardware address. You can change its IP address. To change a MAC address, you have to change the network card!

MAC address is permanently burnt on your network card.

The Mac Address of the Network Card is hard coded or burnt in to the card. Every card has unique Mac address and it will never match with any another card manufactured by any of the vendors/manufaturers. All Vendors/Manufaturers of Network Cards are alloted a set of addresses which they have to assign to a single card during manufaturing and has not to given to any other card manufactured by that particular vendor. This helps in giving a unique internet address which formed using your IP Address and Mac Address. This will be unique and will never match to any other Network card connected to Internet. This way the originator network card of the Data transmitted on the internet can be traced.

If it is not possible to change it can i mask it or hide it from other websites?

What about smac or other programs do they actually work?

Actually it depends on the card, some cards you can change it from the advanced properties for the NIC card under "Network Address"
just type in the new mac. I know I've done it before !
When I get to work I'll post the links I have on the subjct

Yes, you can change a MAC address. We did it all the time back in the way back (DOS w/NW3.x).

In NT/2k in the cards properties "Locally Administered Address" is the same as MAC.

Now, why are you doing this?